Material inspection and material characterisation can be done using a number of existing techniques. Some examples are radiography, digital radiography, microscopy, computed tomography, etc. These techniques are imaging techniques allowing visualisation of objects and features thereof. One example of current material characterisation is the inspection of diamonds using visible light. As such visible inspection often suffers from internal reflections in the diamond, it is often difficult to determine the exact location of defects or faults in the stone. Nevertheless, appropriate localisation of defects is required in order to correctly process the diamond.
One known characterisation technique for the study of gemstone is described in US2006/0062446. The document describes the use of different X-ray images of an object for characterising contour lines of the object or features therein. The X-ray images are made by providing a relative rotation of the object with respect to the source and the detector. The X-ray images thereby are taken from substantially different angles. In order to obtain a three dimensional image, the X-ray images are introduced in a three-dimensional model of the gemstone's outer contours. Although some other techniques also are available, there is a need for a fast imaging technique allowing to localise features in an object with good resolution and contrast.